Other than your original work around of getvariable, the other option is documented in the help:
set myVar to do shell script "echo $KMVAR_My_KM_Variable"
That should work for international characters.
Other than your original work around of getvariable, the other option is documented in the help:
set myVar to do shell script "echo $KMVAR_My_KM_Variable"
That should work for international characters.